In various applications it is necessary to repetitively produce linear movements. Both precision and wear factors are very important. One type of mechanism that is widely used converts rotary motion into longitudinal, reciprocating motion. For example, the lead screw has been known and used for this purpose for many decades.
In more recent times, the conventional lead screw is often replaced by a ball screw, in which balls positioned between a screw member and a ball housing provide rolling friction in lieu of the pure sliding friction that would result from the operation of the conventional lead screw. Another mechanism for converting rotary motion into linear motion of a reciprocating nature is known as the linear friction driver.
In both of those devices there is a problem which adversely affects operating precision. The problem is that the lead screw--or an equivalent elongated drive member, the shaft of a linear friction driver--experiences lateral deflection at one or more points along its length, thus producing a wobbling or vibrating action during its rotation. The wobble or vibration, in turn, causes small but significant errors in the work process being performed.
Wobble in drive mechanisms can have both translational and rotational components. It is a problem in many types of drives, including the rotary-to-linear converters mentioned above.